In the prior art, there are known sealed and thermally insulative tanks intended to be fixed to a supporting structure and comprising a multi-layered structure consisting of one or more sealing membranes and one or more thermal insulation barriers each of which is interleaved between two sealing membranes or between a sealing membrane and the supporting structure.
One such tank is described in the document WO2014167228, for example. In that document, the sealing membrane of each wall of the tank includes a plurality of metal plates featuring series of corrugations perpendicular to one another. The corrugations therefore enable deformation of the sealing membranes because of the effect of thermal and mechanical loads generated by the fluid stored in the tank.
If the tank is mounted in the double hull of a ship, it generally has a polyhedron shape defined by two octagonal end walls connected to each other by a ceiling wall and a bottom wall that are horizontal, two vertical lateral walls, two upper oblique walls each connecting one of the lateral walls to the ceiling wall and two oblique lower walls each connecting one of the lateral walls to the bottom wall. The two series of corrugations of the sealing membrane of the end walls are respectively oriented horizontally and vertically while the two series of corrugations of the sealing membrane of the other walls are respectively oriented in the longitudinal direction of the tank and perpendicularly to the longitudinal direction of the tank.
At the level of each corner of the tank formed at the intersection between two of the eight walls connecting the two end walls and of each corner formed at the intersection between one of the end walls and one of the bottom, ceiling and laterals walls, one of the series of corrugations of each of the two adjacent walls extends in a direction perpendicular to the edge formed at the intersection between two said adjacent walls. The corrugations of the two adjacent walls therefore face one another and the sealing membrane of the corner arrangement features corrugations that assure continuity of the corrugations of the sealing membranes at the level of the corner zone between the two walls. This continuity of the corrugations therefore makes it possible to impart satisfactory flexibility to the sealing membrane at the level of the corner arrangement and to limit stress concentrations in that area.
However, this kind of continuity is not achieved at the level of the intersections between the end walls and the lower or upper oblique walls. In fact, the direction of the vertical corrugations and likewise that of the horizontal corrugations of the sealing member of each end wall are inclined at an angle of 45° relative to the edge formed at the intersection between the end wall and one of the oblique walls while the direction of the corrugations of said oblique wall is perpendicular to the edge. Thus none of the corrugations of the sealing membrane of the end walls is in line with the corrugations of the lower and upper oblique walls. The absence of any such continuity of the corrugations means that the corner arrangements between one of the oblique walls and one of the end walls constitute stress concentration areas and therefore constitute areas of weakness.